exportfs

 

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exportfs(8)                                           exportfs(8)



NAME
       exportfs - maintain list of NFS exported file systems

SYNOPSIS
       /usr/sbin/exportfs  [-avi]  [-o  options,..] [client:/path
       ..]
       /usr/sbin/exportfs -r [-v]
       /usr/sbin/exportfs [-av] -u [client:/path ..]
       /usr/sbin/exportfs [-v]

DESCRIPTION
       The exportfs command is used to maintain the current table
       of  exported  file systems for NFS. This list is kept in a
       separate file named /var/lib/nfs/xtab  which  is  read  by
       mountd  when a remote host requests access to mount a file
       tree, and parts of the list which are active are  kept  in
       the kernel's export table.

       Normally  this  xtab  file is initialized with the list of
       all  file  systems  named  in  /etc/exports  by   invoking
       exportfs -a.

       However, administrators can choose to add and delete indi­
       vidual file systems without modifying  /etc/exports  using
       exportfs.

       Any export requests which identify a specific host (rather
       than a subnet or netgroup etc) are entered  directly  into
       the  kernel's  export  table  as  well as being written to
       /var/lib/nfs/xtab.  Further, any mount  points  listed  in
       /var/lib/nfs/rmtab  which match a non host-specific export
       request will cause an appropriate  export  entry  for  the
       host given in rmtab to be entered into the kernel's export
       table.

OPTIONS
       -a     Export or unexport all directories.

       -o options,...
              Specify a list of export options in the same manner
              as in exports(5).

       -i     Ignore  the /etc/exports file, so that only default
              options and options given on the command  line  are
              used.

       -r     Reexport    all    directories.   It   synchronizes
              /var/lib/nfs/xtab  with  /etc/exports.  It  removes
              entries in /var/lib/nfs/xtab which are deleted from
              /etc/exports, and remove any entries from the  ker­
              nel export table which are no longer valid.


       -u     Unexport one or more directories.

       -v     Be  verbose.  When exporting or unexporting,
              show what's going on.  When  displaying  the
              current  export  list, also display the list
              of export options.

DISCUSSION
   Exporting Directories
       The first synopsis shows how to invoke the  command
       when  adding new entries to the export table.  When
       using exportfs -a, all  directories  in  exports(5)
       are  added to xtab and the resulting list is pushed
       into the kernel.

       The host:/path argument specifies the directory  to
       export  along  with  the host or hosts to export it
       to. All formats described in  exports(5)  are  sup­
       ported;  to export a directory to the world, simply
       specify :/path.

       The export options for a particular  host/directory
       pair  derive  from several sources.  There is a set
       of default  options  which  can  be  overridden  by
       entries  in  /etc/exports  (unless the -i option is
       given).  In addition, the administrator may overide
       any  options  from these sources using the -o argu­
       ment which takes a comma-separated list of  options
       in  the  same  fashion as one would specify them in
       exports(5).  Thus, exportfs can  also  be  used  to
       modify  the  export  options of an already exported
       directory.

       Modifications of the kernel export  table  used  by
       nfsd(8)  take  place  immediately after parsing the
       command line and updating the xtab file.

       The      default      export      options       are
       async,ro,root_squash,no_delay.

   Unexporting Directories
       The  third  synopsis shows how to unexported a cur­
       rently exported  directory.   When  using  exportfs
       -ua,  all  entries  listed in xtab are removed from
       the kernel export tables, and the file is  cleared.
       This effectively shuts down all NFS activity.

       To  remove individial export entries, one can spec­
       ify a host:/path pair. This deletes  the  specified
       entry  from xtab and removes the corresponding ker­
       nel entry (if any).


   Dumping the Export Table
       Invoking exportfs without further options shows the
       current list of exported file systems.  When giving
       the -v option, the list of flags pertaining to each
       export are shown in addition.

EXAMPLES
       The   following  adds  all  directories  listed  in
       /etc/exports to /var/lib/nfs/xtab  and  pushes  the
       resulting export entries into the kernel:

       # exportfs -a

       To  export  the  /usr/tmp directory to host djando,
       allowing asynchronous writes, one would do this:

       # exportfs -o async django:/usr/tmp

DEPENDENCIES
       Exporting to IP networks, DNS and NIS domains  does
       not  enable clients from these groups to access NFS
       immediately; rather, these  sorts  of  exports  are
       hints to mountd(8) to grant any mount requests from
       these clients.  This is usually not a big  problem,
       because  any existing mounts are preserved in rmtab
       across reboots.

       When unexporting a network  or  domain  entry,  any
       current  exports  to  members of this group will be
       checked against the remaining valid exports and  if
       they  themselves  are  nolonger  valid they will be
       removed.


SEE ALSO
       exports(5), mountd(8)

AUTHORS
       Olaf Kirch, <okir@monad.swb.de>
       Neil Brown, <neilb@cse.unsw.edu.au>




                            7 Sep 1999                exportfs(8)

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